1.5 The Theory Of Plate Tectonics

---

Vocabulary

---

Plates: A section of the lithosphere that slowly moves over the asthenosphere
Scientific Theory: A well tested concept that explains a Plate Tectonics
Plate Tectonics: The theory that pieces of Earth's lithosphere are in constant motion
Faults: A break in the Earth's crust were rocks slip past each other
Transform Boundary: A plate boundary were the plates slip past each other in opposite directions
Divergent Boundary: A plate boundary were the plates move away from each other
Rift Valley: A deep valley were two plates move apart
Convergent Boundary: A plate boundary where two plates move into each other

Outline

---

A Theory of Plate Motion

• This theory explains the formation, movement, and subduction
  • Convection currents rise in the asthenosphere with the lithosphere

Plate Boundaries

• The edges of different pieces of the lithosphere, Earth's rigid shell meets lines called Boundaries
  • Faults are the break in the Earth's Crust

Transform Boundary

• The meaning of transform boundary is when the two plates move past each other in opposite directions
  • Earthquakes occur with transform boundaries

Divergent Boundaries

• The places where the two plates diverge is called divergent boundary
  • Most divergent boundaries occur at the Mid-Ocean Ridge
• A Deep valley is called a Rift Valley
  • Rift Valleys form along different boundaries

Convergent Boundaries

• The place where two plates converge is called convergent boundary
  • When the plates converge they form mountains
    • Collision may bring together continental crust & oceanic crust

The Continents' Slow Dance

• The plates move in at an amazingly slow rate (from about one to ten centimeter per year)
  • About 260 years ago the continents were all together and it formed Pangaea